Water - EQ1 - Flashcards
Where did earths water come from
- carbonaceous chondrite meteorite
Define systems approach
- the hydrological cycle is studied by looking at the balance of inputs & how water is moved between stores by flows
Define stores
- reservoirs where water is held e.g oceans
Define fluxes
- rate of flow between the stores
Define processes
- physical mechanisms that drive the fluxes of water between the stores
Define cryosphere
- areas of the earth where water is frozen into snow or ice
Define transpiration
- the loss of water from vegetation into the atmospphehre involving a change from a liquid to a gas
Define blue water
- water is in rivers, streams, lakes & groundwater in liquid form
- visible part of the hydrological cycle
Define green water
- water stored in the soil & vegetation
- invisible part of the hydrological cycle
Define fossil water
- ancient, deep groundwater, from pluvial wetter periods
Define ground water flow
- the slow transfer of percolated water underground through pervious o rporous rocks
Define groundwater recharge
- a hydrological process where water percolates downward from surface water to groundwater
define renewable water
- water that is replenished by the hydrological cycle within human time scales
define non-renewable water
- groundwater bodies (deep aquifers) that have a negligible rate of recharge on the human timescale
define pervious rock
- allows water to pass through it due to cracks or defects
define porous rock
- allows water to flow through the pores
define residence times
- the average time a water molecule will spebd in a reservoir or store
The global hydrological cycle is the…
…circulation of water around the earth
Why is the global hydrological cycle a closed system
- there is a fixed amount of water in the earth’s atmosphere - estimated at 1385 million km^3
- it does not have any external inputs or outputs, so this volume of water is constant & finite
- water exists in different states within a closed system
- the amount held in each state can vary for physical & human reasons
The cycle is driven by solar & gravitational potential energy, what does this mean
- solar energy causes the water to change state (gas, liquid, solid)
- when the subject is above the earths surface it has GPE, causing rivers to flow downhill and precipitation to fall to the ground
- the energy is converted into kinetic energy as water moves through the system
List 6 water stores
- oceans
- ice caps
- ground water
- rivers & lakes
- soil moisture
- atmospheric moisture
Distribution of the earth’s water
freshwater v saline (saltwater)
- saline - 97.5%
- freshwater - 2.5%
Distribution of freshwater
What can fresh water be divided into
- ice caps & glaciers - 68.7%
- groundwater - 30.1%
- surface water - 0.3%
Distribution of fresh surface water
What can surface water be divided into
- 52% - lakes
- 38% - soil moisture
- 8% - atmospheric water vapour
- 1% - rivers
- 1% - accessible water in plants
What is the global water budget
- the annual balance of water fluxes (flows)
- & the size of the water stores
Describe how fluxes balance the precipitation cycle
- more water falls as precipitation to the land masses than is evaporated
- the balance is made up by river run off - excess water on the land is returned to the sea
- if the precipitation & evaporation budget did not work in this way, the land masses would progressively dry up, & oceans would progressively gain all of the world’s water
What is the residence time of oceans
- 3,600 years
What is the residence time of ice caps
- 15,000 years
What is the residence time of groundwater
- up to 10,000 years for deep ground water
- 100-200 years for shallow
What is the residence time of rivers & lakes
- 2 weeks to 10 years, 50 years for very largescale
What is the residence time of soil moisture
- 2-50 weeks
What is the residence time of atmospheric moisture
- 10 days
What is so critical about the global water budget for humans
- accessible surface water is a mere 1% of all the world’s freshwater, and this is the major source of water for human use
- the smallness of this figure emphasises the important point that water is not the abundant resource,, it is a scarce resource needing careful management
define drainage basin
- area of land drained by a river
- they are sometimes freffered to as a ctahcment area
A drainage basin is a…..within the global hydrological cycle, which is …. with external inputs & outputs
- subsystem
- open
how can drainage basins vary in size
- they can be from a small scale stream & small rivers nestle within the drainage basisns of larger rivers
Define watershed
- the edge of high land surrounding a drainage basin, it marks the boundary between 2 drainage basins
Define source
- the beginning or start of a river
Define confluence
- the point at which 2 rivers or streams join
Define tribituary
- a stream or smaller river which joins a larger stream or river
Define mouth
- the point at which the river meets the sea
What are the 3 features of the water cycle system
- inputs
- flows (processes)
- outputs
Define inputs
- the movement of matter into a system, in the hydrological cycle closed system,
- this is an internal movement into a store only, e.g precipitation
Define outputs
- The movement of matter out of a system
- in the hydrological cycle closed system, this is an internal movemen,t only out of a store e.g evaporation
Define flows
- The amount of matter (or energy) transferred from one place to another
Define stores
- Where matter (or energy) is kept for a relatively long period of time
Define solar energy
- Heat energy from the Sun causes changes in the state of water and drives some of the processes within the hydrological cycle, such as evaporation and wind direction
Define Gravitational Potential energy
- The mass of the Earth exerts a pull on water, causing water to fall as precipitation and rivers to flow downhill back to the ocean (the main store)
define interception
- the retention of water by plants and soils which is subsequently evaporated or absorbed by the vegetation
define infiltration
- the process by which water soaks into, or is absorbed by, the soil
define percolation
- similar to infiltration, but a deeper transfer of water into permeable rocks
define throughflow
- the lateral transfer of water downslope through the soil
define groundwater flow
the very slow transfer of percolated water through pervious (permeable) or porous rocks
define surface runoff
- the movement of water that is unconfined by a channel across the surface of the ground a.k.a. overland flow
define channel flow
takes over as soon as the water enters a river or stream; the flow is confined within a channel
what are the 3 types of precipitation patterns
- orographic (relief)
- frontal
- convectional
what is orographic (relief) rainfall
- caused when humid air is forced to rise over mountains
- when the air cools at higher altitude, moisture condenses, forms clouds and droplets of water which then fall due to gravity
- most rain falls on the slopes facing the wind direction and tops of the mountains, with drier air on the other side (lee) so less rain falls (rain shadow).
what is frontal rainfall
- caused when warm humid air is forced to rise at a warm front or cold front, usually as part of a low pressure system (depression)
- the air cools, condensation takes place, clouds of water droplets form which is followed by rain
what is convectional rainfall
- caused when the ground and lower atmosphere are heated by the Sun’s energy causing rising thermals of air
- humidity in the air condenses when it cools at higher altitude, forms towering cumulo-nimbus clouds, often followed by intense heavy rainfall (thunderstorms)